import datetime
import warnings
from dataclasses import dataclass
from functools import wraps

from django.contrib.sites.shortcuts import get_current_site
from django.core.paginator import EmptyPage, PageNotAnInteger
from django.http import Http404
from django.template.response import TemplateResponse
from django.urls import reverse
from django.utils import timezone
from django.utils.deprecation import RemovedInDjango50Warning
from django.utils.http import http_date


@dataclass
class SitemapIndexItem:
    location: str
    last_mod: bool = None

    # RemovedInDjango50Warning
    def __str__(self):
        msg = 'Calling `__str__` on SitemapIndexItem is deprecated, use the `location` attribute instead.'
        warnings.warn(msg, RemovedInDjango50Warning, stacklevel=2)
        return self.location


def x_robots_tag(func):
    @wraps(func)
    def inner(request, *args, **kwargs):
        response = func(request, *args, **kwargs)
        response.headers['X-Robots-Tag'] = 'noindex, noodp, noarchive'
        return response
    return inner


def _get_latest_lastmod(current_lastmod, new_lastmod):
    """
    Returns the latest `lastmod` where `lastmod` can be either a date or a
    datetime.
    """
    if not isinstance(new_lastmod, datetime.datetime):
        new_lastmod = datetime.datetime.combine(new_lastmod, datetime.time.min)
    if timezone.is_naive(new_lastmod):
        new_lastmod = timezone.make_aware(new_lastmod, timezone.utc)
    return new_lastmod if current_lastmod is None else max(current_lastmod, new_lastmod)


@x_robots_tag
def index(request, sitemaps,
          template_name='sitemap_index.xml', content_type='application/xml',
          sitemap_url_name='django.contrib.sitemaps.views.sitemap'):

    req_protocol = request.scheme
    req_site = get_current_site(request)

    sites = []  # all sections' sitemap URLs
    all_indexes_lastmod = True
    latest_lastmod = None
    for section, site in sitemaps.items():
        # For each section label, add links of all pages of its sitemap
        # (usually generated by the `sitemap` view).
        if callable(site):
            site = site()
        protocol = req_protocol if site.protocol is None else site.protocol
        sitemap_url = reverse(sitemap_url_name, kwargs={'section': section})
        absolute_url = '%s://%s%s' % (protocol, req_site.domain, sitemap_url)
        site_lastmod = site.get_latest_lastmod()
        if all_indexes_lastmod:
            if site_lastmod is not None:
                latest_lastmod = _get_latest_lastmod(latest_lastmod, site_lastmod)
            else:
                all_indexes_lastmod = False
        sites.append(SitemapIndexItem(absolute_url, site_lastmod))
        # Add links to all pages of the sitemap.
        for page in range(2, site.paginator.num_pages + 1):
            sites.append(SitemapIndexItem('%s?p=%s' % (absolute_url, page), site_lastmod))
    # If lastmod is defined for all sites, set header so as
    # ConditionalGetMiddleware is able to send 304 NOT MODIFIED
    if all_indexes_lastmod and latest_lastmod:
        headers = {'Last-Modified': http_date(latest_lastmod.timestamp())}
    else:
        headers = None
    return TemplateResponse(
        request,
        template_name,
        {'sitemaps': sites},
        content_type=content_type,
        headers=headers,
    )


@x_robots_tag
def sitemap(request, sitemaps, section=None,
            template_name='sitemap.xml', content_type='application/xml'):

    req_protocol = request.scheme
    req_site = get_current_site(request)

    if section is not None:
        if section not in sitemaps:
            raise Http404("No sitemap available for section: %r" % section)
        maps = [sitemaps[section]]
    else:
        maps = sitemaps.values()
    page = request.GET.get("p", 1)

    lastmod = None
    all_sites_lastmod = True
    urls = []
    for site in maps:
        try:
            if callable(site):
                site = site()
            urls.extend(site.get_urls(page=page, site=req_site,
                                      protocol=req_protocol))
            if all_sites_lastmod:
                site_lastmod = getattr(site, 'latest_lastmod', None)
                if site_lastmod is not None:
                    lastmod = _get_latest_lastmod(lastmod, site_lastmod)
                else:
                    all_sites_lastmod = False
        except EmptyPage:
            raise Http404("Page %s empty" % page)
        except PageNotAnInteger:
            raise Http404("No page '%s'" % page)
    # If lastmod is defined for all sites, set header so as
    # ConditionalGetMiddleware is able to send 304 NOT MODIFIED
    if all_sites_lastmod:
        headers = {'Last-Modified': http_date(lastmod.timestamp())} if lastmod else None
    else:
        headers = None
    return TemplateResponse(
        request,
        template_name,
        {'urlset': urls},
        content_type=content_type,
        headers=headers,
    )
